Field of the Invention
The present invention relates to a light amplification device and a laser processing device. In particular, the present invention relates to a technique for emitting a laser pulse stably from a fiber amplifier of a MOPA (Master Oscillator and Power Amplifier) system.
Description of the Background Art
A laser processing device which adopts a MOPA (Master Oscillator and Power Amplifier) system using a light amplifying fiber and uses light from a laser diode (LD) as seed light, allows emitted light's repetition frequency, peak power, pulse width, etc. to be varied independently of each other, and thus characteristically allows an optimal parameter to be easily selected depending on a target to be processed. For example, Japanese Patent Laying-Open No. 2011-181761 discloses a configuration in which a driver is controlled to vary a condition of excitation light in a non emission period so that energy of pulsed light output from a laser processing device can be stabilized regardless of the non emission period's length.
Japanese Patent Laying-Open No. 2012-248615 discloses a light amplification device which operates in response to a value detected by a peak value detector to control power of excitation light (a driver's bias current) in a non light emission period so that the first output light pulse and the last output pulse generated during a light emission period are equal in power.